The present invention relates to the field of display screens. More specifically embodiments of the present invention relate to the field of portable electronic devices, such as personal digital assistants (PDAs), cell phones, pagers, digital watches etc.
Illumination of the display screens was initially a predominant exercise in the digital watch industry. Digital watches had a small display screen and a single light source sufficient to illuminate that limited area, which, often, did not exceed one square inch. Consumer acceptance and the pragmatic use of such technology led to the adoption of screen illumination in the portable computer industry. In today""s portable or hand-held computer industry backlighting systems are widely used to illuminate portable computer""s display screens.
As the portable computer devices grew more popular and more features were added to their initial functions, larger display screens were required. Display screen surface gradually exceeded a few square inches and a single light source was not sufficient to illuminate such a large area. Present portable computers often use more than a single light source and even a multiplicity of light sources cannot efficiently illuminate rather large display screens used in today""s portable computers.
The increase in the size of display screens presented another design issue in illuminating portable computer""s display screens. A single light source or even multiplicity of light sources may result in some bright spots and some dark spots on the display screens. A bright spot may be so bright as to xe2x80x9cwash outxe2x80x9d any character or information displayed on that portion of the display screen, while the dark spot may leave the display screen too dark to read. A uniform dispersion of light across the display screen substantially reduces problems associated with xe2x80x9cbright spotsxe2x80x9d and xe2x80x9cdark spotsxe2x80x9d.
Regardless of the type of the technology employed in providing light sources for illuminating a display screen, the efficient use of power is an immediate concern. Efforts are continuously made to produce an efficient power source; however, provident use of the light source helps elongate the life of a power source supplying power to the light source. Maximum brightness level can be achieved not only by a stronger power source, but also by preventing waste of light emitted from the limited supply of power available. Therefore a need exists to use the light sources available in the most efficient manner.
Additionally, most of the components used to manufacture a portable computer are relatively small and manual assembly of smaller size components is a common practice in the display screen industry. Cost of producing a portable computer can be reduced if the components used in the manufacturing of these devices were more integrated and number of assembly process steps can be reduced.
Thus a need exists for a portable computer system with a uniformly bright display screen which is efficiently illuminated. Furtheremore, a need exists for a portable computer to maintain a clean (i.e., dust and debris free) display screen at all times. Additionally, a need exists for a method to assemble a display screen with a reduced number of steps in the assembly process.
Accordingly, embodiment of the present invention provide an apparatus, which efficiently improves the front-lighting system of handheld computers by reducing light loss along the edges of a planar light guide illuminating a display screen. Furthermore, the present invention provides a method of assembling display screens for portable computers with a minimum number of steps in the assembly process. Additionally, the present invention provides a method of assembly, which results in a portable computer substantially more resilient to the penetration of environmental dust in the display panel area.
These and other objects and advantages of the present invention will no doubt becomes obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiments which are illustrated in the various drawing figures.
A display assembly for portable computers is disclosed. The display assembly includes a display screen, a light source, and a planar light guide having a top and a bottom surface. The planar light guide includes a plurality of microstructures, which are properly placed on either the top surface or the bottom surface of the planar light guide. The display assembly further includes a light bar disposed adjacent to the light source for illuminating the planar light guide. In one embodiment of the present invention a plastic frame, which mechanically supports the display assembly and the planar light guide are combined as a single component.
A display assembly for efficiently improving brightness of a display screen in a portable computer system is disclosed. One embodiment of the present invention discloses molding a planar light guide wherein a plurality of microstructures are properly placed on either the top surface or the bottom surface of the planar light guide. This embodiment of the present invention further discloses molding of a plastic frame which is surrounded with a reflective material around its inner perimeter to contain light within the planar light guide. In one embodiment of the present invention, the planar light guide and the plastic frame are made into a single piece by process of co-molding or insert molding, thus facilitating the assembly process. In another embodiment of the present invention plastic material used to mold the planar light guide and the plastic frame are of different types. Materials used for molding the plastic frame and the planar light guide have a high optical index of refraction difference with respect to one another. In another embodiment of the present invention a reflective material and at least one mechanical structure are inserted in the mold prior to injection of plastic to make the plastic frame portion of the single piece plastic frame and planar light guide.
Still in another embodiment of the present invention, the planar light guide and a light bar are co-molded and a brightness enhancement film may be disposed between the planar light guide and the light bar. Another embodiment of the present invention discloses combination of the planar light guide, the light bar and the reflective material surrounding the light bar to form a single piece, further reducing steps in the assembly process.
By co-molding components together, embodiments of the present invention (1) provide more efficient light distribution over the display screen; (2) provide a more rigid and mechanically robust display assembly and hand-held device; and (3) reduce overall assembly steps required to manufacture the display unit. Assembly is improved because fewer single pieces are involved and the pieces are physically larger to handle.